In the field of construction, concrete is commonly used as a structural material, both in floors and walls. In the process of creating concrete structure it is common to also make some provision for creating pathways through the concrete for a variety of electrical and mechanical services. For example, channels or conduits in the concrete allow for passage of wiring, plumbing and like services from one side of a concrete structure to the opposite side.
One method for creating passageways in concrete slabs involves cutting holes after the concrete has set. This method has several disadvantages including the fact that it is a time-consuming process, and risks damaging the concrete and reinforcing bar that is frequently present inside a slab. Another method has been to use conduits or forms to create the desired channels in concrete slabs. Several examples exist in the prior art describing forms for use in creating voids in concrete slabs through which components such as electrical wiring and plumbing can be later passed as the building is completed. For example, an early example of a hollow form for creating a conduit in a concrete slab is described in U.S. Pat. No. 963,544 (Graeff). The theme of creating hollow channels in concrete structures has been described in yet other patents (e.g., U.S. Pat. No. 1,530,200; Richardson). Similarly, apparatus for maintaining a conduit in a fixed position prior to the pouring of a concrete slab have also been described (U.S. Pat. No. 3,163,909; Williams).
More modern solutions to this problem include placing a hollow form within the space in which a concrete slab is to be poured. The hollow form creates a void in the concrete, which later can be used to pass electrical and mechanical services. In some cases, the form is left in place and so is one use only. In other cases the form can be removed and so is reusable.
These prior art examples of conduits and forms all suffer from various limitations. For example, where forms are not reusable, there is significant waste in material and cost. Even when reusable forms are used, there are still several limitations. For example, when constructing multi-level building it is often the case that electrical and mechanical services will be run from floor to floor to floor. This requires aligning conduit holes in succeeding floors so that the services can follow a straight path and as they ascend or descend within the building.
Also, in cases where it is desired to fill the conduit once services are put in place, prior art apparatus do not easily provide a way in which to accomplish that step. Moreover, when the forms are removed, there is no way in which to easily include reinforcing material such as steel bars to improve the structural performance within the former conduit void.